The present invention relates to a noncontact type IC card and a system therefor and, more particularly, to a system which performs power supply or data communication using electromagnetic induction or an electromagnetic wave. The present invention is used as, e.g., a data carrier, tag, license, identification, electronic money, memory card, prepaid card, telephone card, or the like.
Conventionally available IC cards are classified into a contact type and noncontact type in accordance with the form of the physical interface serving as a communication means to the device (e.g., a read/write device, or questioner and interrogator; to be referred to as a read/write device hereinafter) of the other party of communication.
In a contact type IC card, power supply or data signal transmission to the card is done through an electrical contact. The card becomes operative for the first time when it is inserted into the slot of a read/write device to connect the contacts. Hence, unless the user consciously inserts the card into the slot, the card does not operate. The card is not unconsciously operated.
On the other hand, the mainstream of noncontact type IC cards receives power necessary for the operation of the mounted IC from a read/write device using electromagnetic induction or an electromagnetic wave. If an IC card is moved close to the read/write device during the operation of the read/write device, the IC card may obtain power by electromagnetic induction, automatically actuate the circuit and then start operation. If the cardholder unintentionally moves the card close to the read/write device, data is unconsciously transmitted between the read/write device and the card. This may pose the problem of information leakage or invalid transactions. To solve this problem, in the conventional noncontact type IC card system, generally, a protection means is employed as software or from the viewpoint of operation form for the entire system.
However, for a read/write device manufactured for the purpose of illicit information read, it is impossible to prevent illicitness unless an advanced technical means such as cryptology is used. Hence, cardholders must always take such situation into consideration. Additionally, as IC cards become popular, various read/write devices having the same carrier frequency but different output powers or application purposes are expected to be used. That is, since one person will hold cards of a plurality of systems, interference between systems of different types and operation errors may pose serious problems.
The present invention has been made to solve the above problems, and has as its object to provide a noncontact type IC card which prevents any information leakage, invalid transactions, undesired interference between systems of different types, and operation errors, and a system for the card.
In order to achieve the above object, according to the present invention, there is provided a noncontact type IC card comprising means for receiving an energy of an electromagnetic field radiated from an external device, an integrated circuit which can be operated by driving power supplied by the energy of the electromagnetic field, and a switch provided on the means for receiving the energy of the electromagnetic field to switch an inductance of the means.